Dear Umesh Ji,
E-invoice is nothing but an invoice. For the purpose of e-invoice, changes are made in Rule 48 (Manner of issuing invoice). So, one may construe that e-invoice is just a manner of issuing an invoice, and the original concept of invoicing stand stiff. This means, if one needs to issue an invoice then follows the manner of issuing an e-invoice.
In short, e-invoicing is only in the cases of invoicing [Refer Rule 46. 47 and 48]. The legal concept is of invoice and the format/manner of issuing such invoice is ‘e-invoice'. That is why in bill of supply cases you cannot issue ‘e-invoice'. It’s like can one issue invoice in case of bill of supply, the answer is obviously ‘no’.